"Watch out for" is often replaced just by "watch" - especially in situations where time is critical, as it is here.

"Watch that crossfire, boys!" (Watch the spacing!) In this case, "watch" can simply mean "pay attention to", although it can also mean "watch out for"... However, "watch out for" also means "beware of" or "avoid". If the boys are the ones causing the crossfire, then "watch"="pay attention to" (to keep it under control) is probably the best way to understand it.